The role of cyclic nucleotides in the modulation of protein synthesis in the cellular slime mold Dictyostelium discoideum will be investigated. The effect of exogenous cyclic AMP on the formation and activity of several developmentally regulated enzymes, as well as on enzymes where developmental regulation has not yet been demonstrated, will be studied. An attempt will be made to isolate and characterize proteins with high affinity for cyclic AMP. The ability of such proteins to bind to Dictyostelium chromatin and DNA will also be tested. In related experiments the cyclic nucleotide metabolism in another slime mold of the genus Polysphondelium will be examined with emphasis on the effects of the polypeptide acrasin produced by that organism on the endogenous synthesis of cyclic AMP. BIBLIOGRAPHIC REFERENCES: Tihon, Claude, Goren, M.B., Spitz, Eva, and Rickenberg, H.V. Convenient elimination of trichloroacetic acid prior to radioimmunoassay of cyclic nuceotides. 1977. Anal. Biochem. 80:, in press. Rickenberg, H.V., Tihon, Claude, and Guzel, Omer. The effect of pulses of 3':5' cyclic adenosine monophosphate on enzyme formation in non-aggregated amoebae of Dictyostelium discoideum. 1977. In: Proceedings of the EMBO Workshop on Development and Differentiation in Cellular Slime Moulds, Porte Conte, Sardinia. Elsevier/North-Holland Biomedical Press B.V., in press.